This invention relates to augmented vision systems, and in particular to a front view mirror system wherein an elevated plane mirror reflects a field of view to a lower mirror for use by an operator so positioned that he has no direct "line of sight" access to that field of view essential to success of his operating function.
Modern high speed ultrasonic aircraft and transatmospheric space vehicles depend in large part on transparencies (viz. "windows") for visual cues to the craft commanders charged with piloting the vehicles to conventional runway landings. Streamlining of these crafts' mold lines calls for shallow impact angles on external surfaces and minimal disturbances to flow lines for efficient flight in the atmosphere. This feature of long shallow surfaces and minimal flow line disturbance would require large areas of conventional transparencies for even marginal line of sight access by the pilot to runway surfaces and navigation aids such as beacons and strobed cues. Transparencies are heavier and bulkier than the stronger composites or special high temperature metals use for craft structure and they are less able to contain harmful radiation and reject thermal energy than conventional structural materials. Long, sloping areas necessary to preserve stream lines for forward facing transparencies also compromise optical quality of presentations to crewmembers (viz. "the pilot").
Under constrains of minimizing weight and preserving stream lines, providing a pilot with "out-the-window" vision has become a major design criterion for modern hypersonic aircraft. The current Concorde supersonic transport provides such visibility to its crew through a "droop-nose" arrangement whereby the nose section, forward of the cockpit and flight crew, is hinged downward during its low speed takeoff and landing operations. Rockwell International's XB-70 incorporated a long windshield ramp covering its main forward transparency to preserve streamlines and provide the necessary line-of-sight access of the pilot to his craft's runways when the covering is removed. X-15 hypersonic test vehicles incorporate moveable canopies to provide their pilots visual access to outside scenes of interest while preserving craft streamlines in high speed flight.
The latter two installations were designed to provide compliance with MIL-STD-850, Aircrew Station Vision Requirements for Military Aircraft, which standards are similarly met by the SST, Concorde, a commercial transport, design. For next generation hypersonic, trans-atmospheric space vehicles and high Mach number military fighter craft, the above solutions to vision satisfaction problems are not applicable. High aerodynamic loads, thermodynamic considerations and weight penalties associated with transparencies in structure negate the most basic of considerations that must be made.
Alternatives to direct view systems include periscopes, radar, television cameras, focal plane sensors and others, none of which provides the "feel" required by pilots for guiding their craft at up to 200 miles an hour onto concrete runways only a few craft lengths in width.
Search of the art has failed to provide cues to the system proposed herein where over the nose visibility of highly streamlined craft is achieved with minimal use of transparencies in craft structure.
lo provide transparency quality visibility to pilots of "submerged" cockpit aerospace craft, a combination of two plane mirrors is employed wherein an upper unit is mounted above a reduced area transparency to reflect a forward view of the craft's track to a second plane mirror on the pilot's control console, FIG. 1. The upper mirror is oriented normal to a selected field of view over the vehicle's nose structure and is raised to its operating position by any convenient mechanism providing for its retraction in high speed flight, with preservation of stream lines and reduced frictional resistance. A scene from the upper mirror is reflected down to the pilot's console unit which, in turn, reflects this view to the pilot. Due to the geometrical relationship between the two mirrors, the view seen is not from the vantage point of the actual eye position out is from an "apparent" eye (the virtual eye of the external mirror) location just aft of the external mirror as shown in FIG. 2. The actual angular relationship between the pilot and the viewed objects is, as a result, off normal by only a small parallax factor.
The scene/image provided by the mirrors presents a valid, "one to one" correlation between the pilot's presentation on the lower mirror and the actual external environment. Images appear on the cockpit mirror, not only at the proper size and distance, but also at their proper spatial orientation with respect to the vehicle and each other. Thus, if the aircrewman looks four degrees left and two degrees low, he sees whatever is actually four degrees left another two degrees low of his aircraft. He is able to expand his field of view by leaning in any direction as he would with a full size transparency with no sacrifice of clarity, spatial orientation or apparent image size.
Such a system provides a high resolution, undistorted three dimension color image of the vehicle's forward motion track. The design and geometry of the optics is simple in the extreme, using existing technology and requiring little development to adapt to different flight vehicles or terrestrial units with similar control problems. Its mirrors provide an accurate, real-world image which appears to the pilot as one viewed from the vantage of the "apparent eye" position. All cues for depth perception are intact. The mirrors can be used in conjunction with small side windows so that the pilot's view would be a panoramic composite of the forward space volume.
Minor modifications to the console ("lower") mirror for semi transparency could provide for presentation of flight instrumentation overlying the craft's approach view, i.e. a heads-Up-Display or HUD.
Accordingly, it is an object of this invention to provide the pilot of a hypersonic aerospace craft, operating in a submerged cockpit, with a real-time, real-world, three dimensional view of space over the nose of his craft, while preserving craft streamlines at high speed flight and minimizing use of transparencies in craft structure.
A further advantage of the vision augmentation system is to increase pilot safety through minimizing bird strike danger through his placement in a submerged cockpit, with minimal transparencies, while retaining three dimensional cues for landing and takeoff procedures. The reduced transparency surface area also decreases the vehicle's observable "signature", simplifying the need for protective radar and laser coatings.